Pd(II)-Catalyzed One-Pot Multiple C-C Bond Formation: En Route Synthesis of Succinimide-Fused Unsymmetrical 9,10-Dihydrophenanthrenes from Aryl Iodides and Maleimides

Developing a straightforward route toward the synthesis of arylaminomaleimides by palladium-catalyzed arylation of one-pot synthesized aminomaleimides

3-Aryl-4-aminomaleimides have well-demonstrated applications, such as being used as fluorophores and inhibitors. However, their previous synthesis methods have involved tedious multi-step procedures or methods that need pre-functionalized maleimides and toxic or unstable reagents. Here, a feasible method is developed to synthesize these useful compounds. This includes the one-pot preparation of 3-aminomaleimides, followed by their direct arylation through a palladium-catalyzed Heck reaction with various aryl iodides regioselectively at the β-position of their amine substituents. The results show that this method efficiently exhibits a broad scope.

Palladium-Catalyzed [3 + 2] Annulation of ortho-Substituted Iodoarenes with Maleimides via a Consecutive Double Heck-type Strategy

Herein, we report an efficient [3 + 2] annulation of ortho-substituted iodoarenes with maleimides via a palladium-catalyzed consecutive double Heck-type strategy, leading to fused tricyclic frameworks of pharmaceutical relevance. The protocol ensued through consecutive inter- and intramolecular Heck couplings effectively. This approach was compatible with a large variety of substrates and functional groups, and it was remarkably tolerated with unprotected maleimide.

Iodide-Dependent Selective Dehydroaromatization Affording Maleimide-Fused 9,10-Phenanthrenes and Their Analogues

A novel and selective synthesis of polycyclic fused maleimides from easily available raw materials under metal-free conditions is presented. This cascade protocol involves self-condensation of cyclohexanones, followed by Diels-Alder reaction with maleimides, intramolecular dehydration, and selective dehydroaromatization in a one-pot fashion, affording maleimide-fused 9,10-phenanthrenes and their analogues in satisfactory yields. Notably, iodide reagents play a critical role in switching the selectivity toward full or partial dehydrogenation compounds.

Rh(III)-Catalyzed Spiroannulation Reaction of N-Aryl Nitrones with 2-Diazo-1,3-indandiones: Synthesis of Spirocyclic Indole-N-oxides and Their 1,3-Dipolar Cycloaddition with Maleimides

An efficient strategy for the preparation of spirocyclic indole-N-oxide compounds through a Rh(III)-catalyzed [4 + 1] spiroannulation reaction of N-aryl nitrones with 2-diazo-1,3-indandiones as C1 synthons under extremely mild conditions is presented. From this reaction, 40 spirocyclic indole-N-oxides were easily obtained in up to 98% yield. In addition, the title compounds could be successfully used for the construction of structurally intriguing maleimide-containing fused polycyclic scaffolds via a diastereoselective 1,3-dipolar cycloaddition reaction with maleimides.

Chemodivergent Synthesis of Indeno[1,2-b]indoles and Isoindolo[2,1-a]indoles via Mn(III)-Mediated or Electrochemical Intramolecular Radical Cross-Dehydrogenative Coupling

Chemodivergent synthesis of indeno[1,2-b]indoles and isoindolo[2,1-a]indoles from the same starting materials involving radical cross-dehydrogenative couplings have been developed. Mn(OAc)₃·2H₂O selectively promoted an intramolecular radical C-H/C-H dehydrogenative coupling reaction to provide indeno[1,2-b]indoles, while an intramolecular radical C-H/N-H dehydrogenative coupling reaction could proceed via electrochemistry to deliver isoindolo[2,1-a]indoles. Plausible mechanisms of the chemodivergent reactions were proposed.

Ligand-Enabled C-H Olefination and Lactonization of Benzoic Acids and Phenylacetic Acids via Palladium Catalyst

A novel ligand propan-2-one O-(p-tolylcarbamoyl) oxime (L7) has been developed to promote C(sp²)-H olefination of benzoic acids and phenylacetic acids via a palladium catalyst. With the subsequent lactonization of the olefinated products through 1,4-addition, highly monoselective cyclic lactone products of benzofuranones and benzopyrones were obtained in moderate to excellent yields. The DFT calculation demonstrated that the novel ligand propan-2-one O-(p-tolylcarbamoyl) oxime (L7) could improve the C-H activation reaction to give cyclic lactone products elegantly.